As is known in the art, a rotary switch typically includes a contact mechanism in which a plated rolling contact is disposed in a rotor. An insulator is disposed between the rolling contact and a spring. The rotor and rolling contact are disposed in a switch housing having a mechanical stop cast therein to provide the rotor having a predetermined mechanical travel. The insulator prevents the spring from wearing away the contact plating. The switch contacts are typically disposed on one end of the switch housing and provide electrical contact between a pair of terminals in a system to which the switch is connected.
Such rotary switches may be used, for example, in computer systems, cash registers, security systems or in any other applications which may utilize a switch to engage and disengage an electrical contact between two terminals. In many applications such switches are used to alternately turn the systems on and off. Thus, in those applications, the rotary switch may be used to engage and disengage operating power from the systems.
As is also known in the art, electrostatic charges typically in the range of 6 kilovolts to 20 kilovolts or more can easily accumulate on a person working in a modern office environment particularly where extensive use is made of synthetic carpeting. Thus, one problem with rotary switches is that such electrostatic charges accumulate on the user of the system and discharge from the user to metal portions of the switch housing or to contact terminals connected to the system.
Such electrical discharge may provide an electric shock to the user and may also result in temporary or permanent damage to the rotary switch or to electrical components within the system to which the switch is connected. To prevent such electrostatic discharge (ESD) from being conducted between a user and the switch contacts, the distance between the charged surface and the switch contacts is often maximized. One problem with this approach however is the concomitant increase required in the length of the rotary switch to prevent the electrostatic discharge from occurring.
Furthermore, electrical arcs may occur due to disconnecting a circuit in which a current typically of about 1 ampere or more is flowing. Such arcs may soften or even melt a material from which the base is made or and plating of the switch contact. When the base material and plating is in such a melted state, the shape of the material may be changed due to the arc or due to mechanical components contacting the base while the base material is in a malleable state. The surface of the disc may thus be disrupted thereby preventing the intended rolling between the rolling contact and the rotor.
Rotary switches may also be provided as a so-called keylock rotary switch having a lock body and a lock cylinder. In the keylock rotary switch, the stop feature is generally die cast into the lock body and cylinder. Thus, keylock switches having unique mechanical travels require unique lock bodies.